Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A transport system includes a plurality of automated guided vehicles that
run on a first track to transport an article, a second track connected to
the first track on which the plurality of automated guided vehicles wait,
a transport controlling apparatus which calculates transport time by
using transport completion information received from the automated guided
vehicle, and a vehicle managing apparatus which controls the number of
automated guided vehicles running on the first track according to a
result of calculation by using transport implementation information
containing the transport time and historical data containing a list of
the transport implementation information.

Claims:

1. A transport system, comprising:a plurality of automated guided vehicles
that run on a first track to transport an article;a second track
connected to the first track on which said plurality of automated guided
vehicles wait;a transport controlling apparatus; anda vehicle managing
apparatus,wherein said plurality of automated guided vehicles transmit
transport completion information including a vehicle ID for
identification of each of said plurality of automated guided vehicles, a
transport start time and a transport end time to said transport
controlling apparatus when said automated guided vehicles complete
transport of said article under control of said transport controlling
apparatus,said transport controlling apparatus includes a first control
section that calculates transport time from said transport start time to
said transport end time and transmits transport implementation
information including the transport time and said vehicle ID to said
vehicle managing apparatus when said transport completion information is
received, andsaid vehicle managing apparatus includes:a storage section
that stores historical data that contains a list of said transport
implementation information; anda second control section that stores said
transport implementation information in said storage section when said
transport implementation information is received, calculates the total
number of times that said article has been transported and an average
value of said transport time from said historical data, and controls the
number of automated guided vehicles running on said first track according
to said total number and said average value through said transport
controlling apparatus.

2. The transport system according to claim 1, wherein in said vehicle
managing apparatus,said storage section stores setting data including an
upper limit value and a lower limit value of the number of running
automated guided vehicles and a reference value of said transport time
previously determined and associated with said total number, andsaid
second control section reads out said reference value associated with
said total number from said setting data, compares said reference value
with said average value, reads out said upper limit value associated with
said total number and compares said upper limit value with the number of
running automated guided vehicles if said average value is higher than
said reference value, and designates a number of automated guided
vehicles equal to the number of running automated guided vehicles minus
said upper limit value among said automated guided vehicles running on
said first track and causes said transport controlling apparatus to
transmit a removal signal to designated automated guided vehicles to
instruct them to move to said second track from said first track, if the
number of running automated guided vehicles is higher than said upper
limit value.

3. The transport system according to claim 2, wherein in said vehicle
managing apparatus,said second control section reads out said lower limit
value associated with calculated said total number from said setting data
and compares said lower limit value with said number of running automated
guided vehicles if the number of running automated guided vehicles is
lower than said upper limit value, and designates a number of automated
guided vehicles equal to said lower limit value minus the number of
running automated guided vehicles among said automated guided vehicles
waiting on said second track and causes said transport controlling
apparatus to transmit an entry signal to designated automated guided
vehicles to instruct them to move to said first track from said second
track, if the number of running automated guided vehicles is lower than
said lower limit value.

4. The transport system according to claim 3, further comprising:a stocker
that stores said article; anda manufacturing apparatus,wherein said
plurality of automated guided vehicles run on said first track and
transport said article from said stocker to said manufacturing
apparatus,said transport controlling apparatus includes a storage section
that stores distance data that indicates a distance from said stocker to
said manufacturing apparatus, andwhen said first control section receives
said transport completion information, said first control section reads
out a transport distance for said automated guided vehicle that transmits
said transport completion information from said distance data and
transmits said transport distance, said transport time and said vehicle
ID to said vehicle managing apparatus as said transport implementation
information, andin said vehicle managing apparatus, said second control
section designates said automated guided vehicles running on said first
track in descending order of a running distance, which is the sum of said
transport distance, based on said historical data, and designates said
automated guided vehicles waiting on said second track in ascending order
of said running distance based on said historical data.

5. A vehicle managing apparatus that forms a system in conjunction with a
plurality of automated guided vehicles that run on a first track and
transport an article, a second track connected to said first track on
which said plurality of automated guided vehicles wait, and a transport
controlling apparatus,wherein said plurality of automated guided vehicles
transmit transport completion information including a vehicle ID for
identification of each of said plurality of automated guided vehicles, a
transport start time and a transport end time to said transport
controlling apparatus when said automated guided vehicles complete
transport of said article under control of said transport controlling
apparatus,said transport controlling apparatus includes control means
that calculates transport time from said transport start time to said
transport end time and transmits transport implementation information
including said transport time and said vehicle ID to said vehicle
managing apparatus when said transport completion information is
received, andsaid vehicle managing apparatus includes:a storage section
that stores historical data that contains a list of said transport
implementation information; anda control section that stores said
transport implementation information in said storage section when said
transport implementation information is received, calculates the total
number of times that said article has been transported and an average
value of said transport time from said historical data, and controls the
number of automated guided vehicles running on said first track according
to said total number and said average value through said transport
controlling apparatus.

6. The vehicle managing apparatus according to claim 5, wherein said
storage section stores setting data including an upper limit value and a
lower limit value of the number of running automated guided vehicles and
a reference value of said transport time previously determined and
associated with said total number, andsaid control section reads out said
reference value associated with said total number from said setting data,
compares said reference value with said average value, reads out said
upper limit value associated with said total number from said setting
data and compares said upper limit value with the number of running
automated guided vehicles if said average value is higher than said
reference value, and designates a number of automated guided vehicles
equal to the number of running automated guided vehicles minus said upper
limit value among said automated guided vehicles running on said first
track and causes said transport controlling apparatus to transmit a
removal signal to designated automated guided vehicles to instruct them
to move to said second track from said first track, if the number of
running automated guided vehicles is higher than said upper limit value.

7. The vehicle managing apparatus according to claim 6, wherein said
control section reads out said lower limit value associated with
calculated said total number from said setting data and compares said
lower limit value with said number of running automated guided vehicles
if the number of running automated guided vehicles is lower than said
upper limit value, and designates a number of automated guided vehicles
equal to said lower limit value minus the number of running automated
guided vehicles among said automated guided vehicles waiting on said
second track and causes said transport controlling apparatus to transmit
an entry signal to designated automated guided vehicles to instruct them
to move to said first track from said second track, if the number of
running automated guided vehicles is lower than said lower limit value.

8. The vehicle managing apparatus according to claim 6, further
comprising:alarm means,wherein said control section repeats a process
including calculating said average value after said removal signal is
transmitted, designating one of said automated guided vehicles running on
said first track if said average value is higher than said reference
value, and causing said transport controlling apparatus to transmit said
removal signal to designated automated guided vehicle until the number of
running automated guided vehicles reaches said lower limit value and
activates said alarm means when the number of running automated guided
vehicles becomes lower than said lower limit value.

9. The vehicle managing apparatus according to claim 7, further
comprising:alarm means,wherein said control section repeats a process
including calculating said average value after said removal signal is
transmitted, designating one of said automated guided vehicles running on
said first track if said average value is higher than said reference
value, and causing said transport controlling apparatus to transmit said
removal signal to designated automated guided vehicle until the number of
running automated guided vehicles reaches said lower limit value and
activates said alarm means when the number of running automated guided
vehicles becomes lower than said lower limit value.

10. The vehicle managing apparatus according to claim 8, wherein said
control section repeats a process including calculating said average
value after said entry signal is transmitted, designating one of said
automated guided vehicles waiting on said second track if said average
value is higher than said reference value, and causing said transport
controlling apparatus to transmit said entry signal to designated
automated guided vehicle until the number of running automated guided
vehicles reaches said upper limit value and activates said alarm means
when the number of running automated guided vehicles becomes higher than
said upper limit value.

11. The vehicle managing apparatus according to claim 9, wherein said
control section repeats a process including calculating said average
value after said entry signal is transmitted, designating one of said
automated guided vehicles waiting on said second track if said average
value is higher than said reference value, and causing said transport
controlling apparatus to transmit said entry signal to designated
automated guided vehicle until the number of running automated guided
vehicles reaches said upper limit value and activates said alarm means
when the number of running automated guided vehicles becomes higher than
said upper limit value.

12. The vehicle managing apparatus according to claim 6, wherein said
plurality of automated guided vehicles run on said first track and
transport said article from a stocker to a manufacturing apparatus, andin
the case where said transport controlling apparatus includes storage
means that stores distance data that indicates a distance from said
stocker to said manufacturing apparatus, and when said control means
receives said transport completion information, said first control
section reads out a transport distance for said automated guided vehicle
that transmits said transport completion information from said distance
data and transmits said transport distance, the transport time and the
vehicle ID to said vehicle managing apparatus as said transport
implementation information,said control section designates said automated
guided vehicles running on said first track in descending order of a
running distance, which is the sum of said transport distance, based on
said historical data, and designates said automated guided vehicles
waiting on said second track in ascending order of said running distance
based on said historical data.

13. The vehicle managing apparatus according to claim 7, wherein said
plurality of automated guided vehicles run on said first track and
transport said article from a stocker to a manufacturing apparatus, andin
the case where said transport controlling apparatus includes storage
means that stores distance data that indicates a distance from said
stocker to said manufacturing apparatus, and when said control means
receives said transport completion information, said first control
section reads out a transport distance for said automated guided vehicle
that transmits said transport completion information from said distance
data and transmits said transport distance, the transport time and the
vehicle ID to said vehicle managing apparatus as said transport
implementation information,said control section designates said automated
guided vehicles running on said first track in descending order of a
running distance, which is the sum of said transport distance, based on
said historical data, and designates said automated guided vehicles
waiting on said second track in ascending order of said running distance
based on said historical data.

14. The vehicle managing apparatus according to claim 8, wherein said
plurality of automated guided vehicles run on said first track and
transport said article from a stocker to a manufacturing apparatus, andin
the case where said transport controlling apparatus includes storage
means that stores distance data that indicates a distance from said
stocker to said manufacturing apparatus, and when said control means
receives said transport completion information, said first control
section reads out a transport distance for said automated guided vehicle
that transmits said transport completion information from said distance
data and transmits said transport distance, the transport time and the
vehicle ID to said vehicle managing apparatus as said transport
implementation information,said control section designates said automated
guided vehicles running on said first track in descending order of a
running distance, which is the sum of said transport distance, based on
said historical data, and designates said automated guided vehicles
waiting on said second track in ascending order of said running distance
based on said historical data.

15. The vehicle managing apparatus according to claim 9, wherein said
plurality of automated guided vehicles run on said first track and
transport said article from a stocker to a manufacturing apparatus, andin
the case where said transport controlling apparatus includes storage
means that stores distance data that indicates a distance from said
stocker to said manufacturing apparatus, and when said control means
receives said transport completion information, said first control
section reads out a transport distance for said automated guided vehicle
that transmits said transport completion information from said distance
data and transmits said transport distance, the transport time and the
vehicle ID to said vehicle managing apparatus as said transport
implementation information,said control section designates said automated
guided vehicles running on said first track in descending order of a
running distance, which is the sum of said transport distance, based on
said historical data, and designates said automated guided vehicles
waiting on said second track in ascending order of said running distance
based on said historical data.

16. The vehicle managing apparatus according to claim 10, wherein said
plurality of automated guided vehicles run on said first track and
transport said article from a stocker to a manufacturing apparatus, andin
the case where said transport controlling apparatus includes storage
means that stores distance data that indicates a distance from said
stocker to said manufacturing apparatus, and when said control means
receives said transport completion information, said first control
section reads out a transport distance for said automated guided vehicle
that transmits said transport completion information from said distance
data and transmits said transport distance, the transport time and the
vehicle ID to said vehicle managing apparatus as said transport
implementation information,said control section designates said automated
guided vehicles running on said first track in descending order of a
running distance, which is the sum of said transport distance, based on
said historical data, and designates said automated guided vehicles
waiting on said second track in ascending order of said running distance
based on said historical data.

17. The vehicle managing apparatus according to claim 11, wherein said
plurality of automated guided vehicles run on said first track and
transport said article from a stocker to a manufacturing apparatus, andin
the case where said transport controlling apparatus includes storage
means that stores distance data that indicates a distance from said
stocker to said manufacturing apparatus, and when said control means
receives said transport completion information, said first control
section reads out a transport distance for said automated guided vehicle
that transmits said transport completion information from said distance
data and transmits said transport distance, the transport time and the
vehicle ID to said vehicle managing apparatus as said transport
implementation information,said control section designates said automated
guided vehicles running on said first track in descending order of a
running distance, which is the sum of said transport distance, based on
said historical data, and designates said automated guided vehicles
waiting on said second track in ascending order of said running distance
based on said historical data.

18. A transport controlling method that is implemented in a system
including a plurality of automated guided vehicles that run on a first
track to transport an article, a second track connected to said first
track on which said plurality of automated guided vehicles wait, a
transport controlling apparatus, and a vehicle managing apparatus, said
method comprising:said plurality of automated guided vehicles
transmitting transport completion information including a vehicle ID for
identification of each of said plurality of automated guided vehicles, a
transport start time and a transport end time to said transport
controlling apparatus when said automated guided vehicles complete
transport of said article under control of said transport controlling
apparatus,said transport controlling apparatus calculating transport time
from said transport start time to said transport end time and
transmitting transport implementation information including said
transport time and said vehicle ID to said vehicle managing apparatus
when said transport completion information is received, andsaid vehicle
managing apparatus calculating the total number of times that said
article has been transported and an average value of said transport time
based on data that contains a list of said transport implementation
information, and controlling the number of automated guided vehicles
running on said first track according to said total number and said
average value through said transport controlling apparatus.

Description:

[0001]This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2007-257619 filed on Oct. 1, 2007,
the content of which is incorporated by reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to a transport system, a vehicle
managing apparatus, and a transport controlling method that use an
automated guided vehicle running on a track to transport an article.

[0004]2. Description of Related Art

[0005]In some manufacturing lines (e.g., a semiconductor fabrication
line), tracks installed on a ceiling extend from automated storages
(stockers) to manufacturing apparatuses, and automated guided vehicles
running on the tracks transport articles (e.g., semiconductor wafers)
from the automated storages to the manufacturing apparatuses.

[0006]There have been proposed various kinds of systems designed to reduce
a transport time in a situation where a plurality of automated guided
vehicles are used to transport articles. Japanese Patent Laid-Open No.
2000-353015 (hereinafter referred to as Patent document 1) discloses an
example of such systems.

[0007]In a situation where a track for automated guided vehicles includes
a main line and a branch line, and automated storages are located along
the branch line, if an automated guided vehicle returning to the main
line from the branch line after storing an article in the automated
storage runs into another automated guided vehicle running on the main
line at the junction of the branch line and the main line, one of the
automated guided vehicles has to wait for the other to pass through the
junction. The system disclosed in Patent document 1 is intended to solve
the problem.

[0008]The system disclosed in Patent document 1 has a main line having the
shape of a loop, a branch line connected to the main line at two points,
that is, a branch point and a junction point, a plurality of automated
guided vehicles that run in one direction on the main line and the branch
line, automated storages located along the branch line, and a transport
controller.

[0009]In the system disclosed in Patent document 1, in response to a
transport instruction from the transport controller, a first automated
guided vehicle runs into the branch line from the main line via the
branch point and transports the article to the location of the automated
storage. The article is carried into the automated storage, and after
that, the first automated guided vehicle waits for the next instruction
from the transport controller.

[0010]Then, when a second automated guided vehicle passes through a
communication point that is located upstream of the branch point in the
main line, the second automated guided vehicle reports to the transport
controller that the second automated guided vehicle has passed through
the communication point. In response to the passage report, the transport
controller checks the destination of the second automated guided vehicle.
Then, if the destination is the location where the first automated guided
vehicle is waiting, the transport controller transmits a move instruction
to the first automated guided vehicle. In response to the move
instruction, the first automated guided vehicle runs back into the main
line from the branch line via the junction point and moves to another
waiting location designated by the move instruction.

[0011]As described above, in the system disclosed in Patent document 1, an
automated guided vehicle waiting on the branch line starts moving to the
junction point when another automated guided vehicle that receives an
instruction to transport an article to the automated storage located
along the branch line passes through the communication point. As a
result, no waiting time occurs when the automated guided vehicle passes
through the junction point, and the transport time is reduced
accordingly.

[0012]In the case where a plurality of automated guided vehicles are used
to transport articles, the number of automated guided vehicles and the
transport time are related as shown in FIG. 1, for example. In FIG. 1,
dotted line 601 shows a case where the total number of times of transport
is 2000, and soild line 602 shows a case where the total number of times
of transport is 3000. "Number of times transport" equals number of times
that an article has been transported.

[0013]As can be seen from FIG. 1, the transport time does not always
decrease as the number of automated guided vehicles increases. On the
contrary, if there are too many automated guided vehicles, the transport
time can increase because of congestion on the track. In addition, as can
be seen from FIG. 1, the optimal number of automated guided vehicles can
vary with the number of times of transport.

[0014]In general, in a manufacturing line in which automated guided
vehicles running on a track transport articles, the number of automated
guided vehicles is fixed. However, the number of times of transport can
vary according to the manufacturing condition, so that there is a problem
that the transport time can increase depending on the number of automated
guided vehicles.

[0015]Patent document 1 also does not disclose any arrangement to control
the number of automated guided vehicles according to the number of times
of transport. Therefore, it is considered that the problem described
above can occur in the system disclosed in Patent document 1.

SUMMARY

[0016]In one embodiment, there is provided a transport system that
includes a plurality of automated guided vehicles that run on a first
track to transport an article, a second track connected to the first
track on which the plurality of automated guided vehicles wait, a
transport controlling apparatus which calculates transport time by using
transport completion information received from the automated guided
vehicle, and a vehicle managing apparatus which calculates the total
number of times that the article has been transported and an average
value of the transport time from historical data containing a list of
transport implementation information including the transport time
received from the transport controlling apparatus and controls the number
of automated guided vehicles running on the first track according to the
total number and the average value.

[0017]According to the present invention, the second track connected to
the first track for transporting an article on which the plurality of
automated guided vehicles wait is provided. In addition, the vehicle
managing apparatus monitors the total number of times of the transport
and the average value of the transport time and controls the number of
automated guided vehicles running on the first track based on the values.
Thus, when the number of times of transport varies, the number of
automated guided vehicles transporting articles is optimized. As a
result, the transport time can be optimized according to the variation of
the number of times of transport.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]The above features and advantages of the present invention will be
more apparent from the following description of certain preferred
embodiments taken in conjunction with the accompanying drawings, in
which:

[0019]FIG. 1 is a graph showing a relationship between the number of
automated guided vehicles and the transport time;

[0020]FIG. 2 is a block diagram showing an exemplary configuration of a
vehicle managing apparatus and a transport controlling apparatus
according to an exemplary embodiment;

[0021]FIG. 3 is a diagram showing an exemplary layout of a manufacturing
line in a factory in which a transport system according to the exemplary
embodiment is used for transport;

[0022]FIG. 4 is a diagram showing an example of data stored in a storage
section of the transport controlling apparatus according to the exemplary
embodiment;

[0023]FIGS. 5A and 5B are diagrams showing examples of data stored in a
storage section of the vehicle managing apparatus according to the
exemplary embodiment; and

[0024]FIG. 6 is a flowchart for illustrating a procedure of controlling
the number of running automated guided vehicles.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025]The invention will be now described herein with reference to
illustrative embodiments. Those skilled in the art will recognize that
many alternative embodiments can be accomplished using the teachings of
the present invention and that the invention is not limited to the
embodiments illustrated for explanatory purposes.

[0026]Referring now to FIGS. 2 and 3, a transport system according to a
first exemplary embodiment of the present invention includes vehicle
managing apparatus 1, transport controlling apparatus 2, a plurality of
automated guided vehicles including automated guided vehicle 3, and
waiting rail 72 on which the plurality of automated guided vehicle wait.

[0027]In addition, in this exemplary embodiment, transport rail 71 and
waiting rail 72 shown in FIG. 3 are installed on the ceiling of the
factory, and stocker 41 for storing an article and manufacturing
apparatuses 51 to 62 are located along transport rail 71. In FIG. 3, a
manufacturing apparatus is described as "MA".

[0028]Automated guided vehicle 3 is an automated guided vehicle provided
with a suspended transport mechanism, such as an overhead hoist transport
(OHT).

[0029]When automated guided vehicle 3 receives a transport signal that
designates the transport source (stocker 41) and the transport
destination from transport controlling apparatus 2, automated guided
vehicle 3 runs on transport rail 71 according to the transport signal to
transport an article. Then, when the transport is completed, automated
guided vehicle 3 transmits transport completion information containing
the vehicle ID thereof, the transport start time and the transport end
time to transport controlling apparatus 2.

[0030]The vehicle ID is intended to identify each of the plurality of
automated guided vehicles and is previously assigned to each automated
guided vehicle.

[0034]FIG. 4 is a diagram showing an example of data stored in storage
section 21.

[0035]As shown in FIG. 4, storage section 21 stores distance data 101 that
indicates the distance (transport distance) on transport rail 71 from
stocker 41 to each of the manufacturing apparatuses 51 to 62 that the
automated guided vehicle runs.

[0036]When control section 22 receives an instruction to transport an
article from a host computer (not shown), control section 22 designates
one of the automated guided vehicles on transport rail 71 and transmits a
transport signal to the designated automated guided vehicle.

[0037]When control section 22 receives transport completion information
from an automated guided vehicle, control section 22 calculates the
transport time from the transport start time to the transport end time.
In addition, control section 22 extracts the transport distance from
distance data 101 stored in storage section 21 based on the transport
source and the transport destination indicated by the transport signal
transmitted to the automated guided vehicle.

[0039]Furthermore, control section 22 transmits the removal signal and the
entry signal to the automated guided vehicle designated by vehicle
managing apparatus 1 under the control of vehicle managing apparatus 1.

[0042]FIG. 5A shows historical data 102 containing a list of transport
implementation information. FIG. 5B shows setting data 103 containing
upper limit values and lower limit values of the number of automated
guided vehicles running on transport rail 71 and reference values of the
transport time for different predetermined total numbers of times of
transport. In FIG. 5B, upper limit value is described as "ULV", low limit
value is described as "LLV".

[0043]Next, an operation of the transport system according to this
exemplary embodiment will be described.

[0044]In this exemplary embodiment, it is assumed that automated guided
vehicle 3 is running on transport rail 71.

[0045]First, an operation of transporting an article will be described.

[0046]When control section 22 of transport controlling apparatus 2
receives an instruction to transport an article from the host computer,
control section 22 designates one of the automated guided vehicles on
transport rail 71 and transmits a transport signal to the designated
automated guided vehicle. In this exemplary embodiment, it is assumed
that automated guided vehicle 3 is designated.

[0049]In this way, the operation of transporting an article is
accomplished.

[0050]Next, an operation of controlling the number of automated guided
vehicles on transport rail 71 (the number of running automated guided
vehicles) will be described.

[0051]FIG. 6 is a flowchart for illustrating the operation of controlling
the number of running automated guided vehicles.

[0052]Control section 12 calculates the total number of times of transport
and the average value of the transport time from historical data 102
(step S1).

[0053]In the processing in step S1, when control section 12 calculates the
total number and the average value is not particularly limited. In this
exemplary embodiment, it is assumed that the processing in step S1 is
performed after a lapse of a predetermined time.

[0054]Then, control section 12 determines whether or not the average value
is equal to or lower than the reference value associated with the
calculated total number by referring to setting data 103 (step S2).

[0055]If the average value is higher than the reference value, control
section 12 determines whether or not the number of running automated
guided vehicles is higher than the upper limit value associated with the
calculated total number by referring to setting data 103 (step S3).

[0056]If the number of running automated guided vehicles is higher than
the upper limit value, control section 12 designates a number of
automated guided vehicles on transport rail 71 equal to the number of
running automated guided vehicles minus the upper limit value, and
transmits an instruction to move the designated automated guided vehicles
to waiting rail 72 and the vehicle IDs of the designated automated guided
vehicles to transport controlling apparatus 2 (step S4).

[0057]Then, control section 22 transmits the removal signal to the
automated guided vehicles designated by control section 12 (step S5).
When a predetermined time elapses after the automated guided vehicles
receiving the removal signal moves to waiting rail 72, control section 22
calculates the average value of the transport time and determines whether
or not the average value is equal to or lower than the reference value
(step S6).

[0058]If the average value is higher than the reference value, control
section 12 designates one of the automated guided vehicles on transport
rail 71 to move to waiting rail 72 and outputs the move instruction and
the vehicle ID of the designated automated guided vehicle to transport
controlling apparatus 2 (step S7)

[0059]The procedure from step S5 to step S7 is repeated until the number
of running automated guided vehicles reaches the lower limit value
associated with the upper limit value compared with the number of running
automated guided vehicles in the processing in step S3 in setting data
103 (step S8).

[0060]If it is determined that the number of running automated guided
vehicles is lower than the upper limit value in the processing in step
S3, control section 12 determines whether or not the number of running
automated guided vehicles is lower than the lower limit value associated
with the upper limit in setting data 103 (step S9).

[0061]If the number of running automated guided vehicles is lower than the
lower limit value, control section 12 designates a number of automated
guided vehicles on waiting rail 72 equal to the lower limit value minus
the number of running automated guided vehicles, and transmits an
instruction to move the designated automated guided vehicles to transport
rail 71 and the vehicle IDs of the designated automated guided vehicles
to transport controlling apparatus 2 (step S10).

[0062]Then, control section 22 transmits the entry signal to the automated
guided vehicles designated by control section 12 (step S11). When a
predetermined time elapses after the automated guided vehicles receiving
the entry signal moves to transport rail 71, control section 22
calculates the average value of the transport time and determines whether
or not the average value is equal to or lower than the reference value
(step S12).

[0063]If the average value is higher than the reference value, control
section 12 designates one of the automated guided vehicles on waiting
rail 72 to move to transport rail 71 and transmits the move instruction
and the vehicle ID of the designated automated guided vehicle to
transport controlling apparatus 2 (step S13).

[0064]The procedure from step S11 to step S13 is repeated until the number
of running automated guided vehicles reaches the upper limit value
associated with the lower limit value compared with the number of running
automated guided vehicles in the processing in step S9 in setting data
103 (step S14).

[0065]If it is determined that the number of running automated guided
vehicles is lower than the lower limit value in the processing in step
S8, or if it is determined that the number of running automated guided
vehicles is higher than the lower limit value in the processing in step
S9, or if it is determined that the number of running automated guided
vehicles is lower than the upper limit value in the processing in step
S14, then control section 12 transmits a control signal to alarm means
13. In response to this, alarm means 13 outputs an alarm sound (step
S15).

[0066]After alarm means 13 outputs the alarm sound, if a user changes the
upper limit value or the lower limit value in setting data 103 through an
input operation on a plurality of keys on operating section 14, control
section 12 rewrites setting data 103 based on the input.

[0067]In the processings in steps S4 and S7, control section 12 designates
the automated guided vehicles in descending order of the running
distance, which is the total transport distance calculated based on
historical data 102. Furthermore, in the processings in steps S10 and
S13, control section 12 designates the automated guided vehicles in
ascending order of the running distance. If the automated guided vehicles
are designated in this way, the running distances of the automated guided
vehicles can be made uniform.

[0068]In this exemplary embodiment, waiting rail 72 connected to transport
rail 71 for transporting an article on which the plurality of automated
guided vehicles wait is provided. In addition, vehicle managing apparatus
1 monitors the total number of times of transport and the average value
of the transport time and controls the number of automated guided
vehicles running on transport rail 71 based on the values. Thus, when the
number of times of transport varies, the number of automated guided
vehicles transporting articles is optimized. As a result, the transport
time can be optimized according to the variation of the number of times
of transport.

[0069]Furthermore, in this exemplary embodiment, since waiting rail 72 is
provided, the distance at which automated guided vehicles, that are not
involved in article transport, are wastefully run, is reduced. As a
result, deterioration due to wear is reduced, so that the time between
maintenance of the automated guided vehicles can be increased. In
addition, the cost of electricity to drive the automated guided vehicles
is reduced, so that the transport cost can also be reduced.

[0070]It is apparent that the present invention is not limited to the
above embodiments, but may be modified and changed without departing from
the scope and spirit of the invention.